Mobile telecommunications routing

ABSTRACT

A telecommunications mobility management system is arranged to allocate a mobile unit to different switching routes for different classes of service, for example to allow services capable of operation over packet-switched and circuit-switched to be managed separately. Separate location updates are transmitted to a register, and flagged for selective retrieval by a routing function when an incoming connection request is made, the appropriate switch ID being selected according to the class of service to which the connection request relates.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a National Phase entry of PCT Application No.PCT/EP2016/054457, filed on 2 Mar. 2016, which claims priority to EPPatent Application No. 15275086.5, filed on 25 Mar. 2015, which arehereby fully incorporated herein by reference.

BACKGROUND

This invention relates to mobile telecommunications systems and inparticular to selective routing of traffic according to type.

TECHNICAL FIELD

There are currently a number of mobile telecommunications technologiesavailable to the general user, offering a variety of services, inparticular voice and data services, using a mixture of circuit-switchedand packet-switched protocols. In general the more established systemshave a wider coverage than newer systems which are still beingintroduced. Typically the newer technology is initially installed in alimited range of small cells where there is a particular need forcoverage, with a partner macrocell network providing circuit-switchedFall Back (CSFB) services. In such an arrangement, in locations whereboth systems are available, network services, such as voice, are routedover a circuit switched network and data over a packet-switched network.

An added complication is that not all mobile user terminals are fullycompatible with all mobile technologies. A particular measure which isused in the Long Term Evolution (LTE) standard is known as “CircuitSwitched Fall Back”, which is a mechanism that allows user terminalsthat do not have a capability to operate Voice-over-LTE (VoLTE)technology, and therefore cannot place voice calls over thepacket-switched LTE (or “4G”) system, to “fall-back” to the oldercircuit-switched 2G or 3G (or “UMTS”) systems to make or receive voicecalls whilst remaining attached to a 4G/LTE packet-switched radio accessnetwork (radio access network) for data services.

SMS text messages can be delivered over the LTE radio access network, ifthe SGs Interface defined in 3GPP TS 29.118 is supported, whereasnon-VoLTE capable devices cannot receive voice calls over the LTE radioaccess network, which is why the Circuit Switched Fallback mechanism isrequired.

Traditionally, voice and text messages have followed the same routethrough the network since they had to be delivered over the same accessnetwork, using the same international mobile subscriber identity (IMSI)and mobile switching center server (MSCS), there being no alternativeradio delivery mechanism for text messaging. However, the 4G systemprovides a way to deliver text messages in a different way to thedelivery method for voice, and for which there is no need for the deviceto fall-back to the 2/3G network, and therefore there is no need toroute the SMS via the Circuit Switched core if it is being delivered viathe 4G RAN.

Current Circuit Switch Fall Back procedures in 3GPP require a dualattachment when users attach to a 4G network, one attachment against the4G Evolved Packet Core (EPC), and a separate IMSI attachment to aMSC/VLR allocated in the Circuit Switched (circuit-switched) voice corefor the purpose of routing voice calls and text messages to the device.When the 2/3G radio access network (and associated circuit-switchedcore) and the 4G radio access network (and associated EPC core) belongto different operators, the allocation of an MSC server in the 2/3Gpartner operator's voice core network also implies that SMS terminatingmessages may have to be routed via the partner's circuit-switched corenetwork, even when the subscriber is attached to its home operator's 4Gradio access network. This is suboptimal since SMS messages would berouted via the 2/3G voice core before final delivery to the UE via the4G access, resulting in an unnecessary dependency on the 2/3G voicecore. There may also be commercial implications when the 4G and 2/3Goperators are not the same.

SUMMARY

The present disclosure accordingly provides a communications routingmanagement entity for a communications network arranged to respond to arouting request relating to a user identity by retrieving a routinginstruction from a database of routing instructions, wherein thecommunications routing management entity is arranged to distinguishbetween a first type of requested communications connection and a secondtype of requested communications connection, and retrieving a firstrouting instruction associated with the first type of requestedcommunications connection and retrieving a second routing instructionassociated with the second type of requested communications connection.

In some embodiments, in response to a routing request relating to theuser identity, a routing instruction is retrieved from a database ofrouting instructions, in which a first routing instruction is retrievedin response to a first type of requested communications connection and asecond routing instruction is retrieved in response to a second type ofrequested communications connection. In one embodiment the first type ofcommunications connection is carried by a circuit-switching protocol andthe second type of communications connection is carried by apacket-switching protocol, and voice calls are directed to the firstcommunications connection and text messages are directed to the secondcommunications connection.

Embodiments of the disclosure therefore propose an intelligent“service-aware routing” function to route incoming requests to differentMSCs depending on whether a routing request is made for a service thatrequires a circuit switched connection (such as voice calls) or for aservice which can be handled by a packet switched connection (e.g. textmessaging). Embodiments of the disclosure may be used in conjunctionwith a “service-aware attachment” function that splits an IMSIattachment into two separate “service-specific” attachments, for exampleone for circuit switching routing and one for packet switched routing,and described in our co-pending International Patent Publication No. WO2016/150669, which claims priority from the same European application asthe present application. These functions may be incorporatedrespectively in the mobile management entities and home subscriberservers of the conventional network, or may be arranged to operate as anintermediary between them.

In this way, embodiments of the disclosure can maintain two separateidentities in the circuit switched domain in a standard circuit-switchedfallback request. In a National roaming scenario, where differentoperators provide 2/3G and 4G respectively, the mechanism included inthis disclosure allows for some types of traffic to be routed directlyvia the 4G network without any involvement from the circuit-switchedvoice core. This can represent a cost saving as well as a reduction inoverall complexity and dependency on the 2/3G operator. One situation inwhich this facility may be used allows text messages to be redirected sothat they can continue to be handled by the core data (4G) networkpacket switched data network, whilst voice traffic unsuitable for the 4Gsystem is handled by the older 2G/3G system.

The service-aware attachment function may be deployed within a mobilemanagement entity and the service-aware routing function may be deployedin a home server associated with the user. Alternatively, both functionsmay reside in a “Virtual Core” attachment management entity that sits inthe interface between a mobile management entity and a mobile switchingcenter, and between a gateway MSC (GMSC) and the Home Location register.Embodiments of both arrangements will be described.

The service-aware attachment function could also act as a “virtual” MSCto route SMS messages to subscribers currently attached to the 4G radioaccess network, avoiding the need for an extra MSC in the networkdedicated to routing SMS messages.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure will now be described, by way ofexample only, with reference to the accompanying drawings, in which:

FIG. 1 is a diagram representing the prior art dual attachment circuitswitched fallback process of the 3GPP TS25.272 standard with which thisembodiment interacts.

FIG. 2 is a diagram representing the prior art voice call connectionprocess.

FIG. 3 is a diagram representing the prior art text message connectionprocess.

FIG. 4 is a diagram representing a dual attachment circuit switchedfallback process according to a first embodiment.

FIG. 5 is a diagram representing a voice call connection processaccording to this first embodiment.

FIG. 6 is a diagram representing a text message connection processaccording to this first embodiment.

FIG. 7 is a diagram representing a dual attachment circuit switchedfallback process according to a second embodiment

FIG. 8 is a diagram representing a voice call connection processaccording to this second embodiment.

FIG. 9 is a diagram representing a text message connection processaccording to this second embodiment in a first condition.

FIG. 10 is a diagram representing a text message connection processaccording to this second embodiment in a second condition.

FIG. 11 is a flow diagram depicting an attachment operation of the firstembodiment.

FIG. 12 is a flow diagram depicting a routing operation of the firstembodiment.

FIG. 13 is a flow diagram depicting an attachment operation of thesecond embodiment.

FIG. 14 is a flow diagram depicting a routing operation of the secondembodiment.

DETAILED DESCRIPTION

The embodiments to be described are intended to be compatible with the3GPP standards, and in particular use outputs from, and provide inputsto, the TS 25.272 Section 5.2 Dual attachment circuit switched fallbackprocess. This process will be summarized here, with reference to FIGS. 1to 3, which show the interactions between a user equipment (UE) 1, amobile management entity (MME) 3, a mobile switching center 4 andassociated visitor location register (VLR) 40 and a home subscriberserver (HSS) 5 during attachment (FIG. 1), and their co-operation with agateway MSC 6 for handling incoming voice calls (FIG. 2) and textmessages (FIG. 3). The HSS stores a concordance 80 between the MSISDNnumbers (directory number) and the IMSI numbers (permanent numberassociated with the Subscriber identity module (SIM) installed in thehandset) for which it is responsible, and routing information for thosehandsets.

Referring first to FIG. 1, when the user equipment (UE) 1 establishes awireless connection through a base station 2 (also known as an evolvedNode B or eNB) to the network infrastructure, it initiates the attachprocedure by the transmission of an Attach Request message 10 to the MME3. The request 10 includes an Attach Type field indicating that the UErequests a combined EPS/IMSI attach and informs the network that the UE1 is capable and configured to use circuit-switched fallback and/or SMSover SGs.

An attach procedure 11 is then followed by the MME 3. If the AttachRequest message includes an Attach Type indicating that the UE 1requests a combined EPS/IMSI attach, the MME 3 allocates a new locationarea identity (LAI) for the UE. The MME 3 derives a VLR number based onthe newly allocated LAI and other data provided by the UE 1.

The MME then initiates a location update procedure by transmitting alocation update (at 16) towards the new MSC/VLR 4, 40 using subscriberdata 80 maintained by the HSS 5. The VLR 40 creates an association withthe MME 3 by storing the MME name. The VLR 40 then performs a LocationUpdating procedure in the circuit-switched domain (at 17), to inform arouting table 80 in the HSS 5 of the new location of the UE 1. Therouting table 80 stores the network identities (IMSI and MSISDN) of theUE 1, and the identity of the currently serving MSC 4.

In this prior art system, incoming voice calls are handled as shown inFIG. 2. An incoming call request is received by a gateway MSC 6 and arouting request is made to the destinations user's HSS 5 (at 20), whichretrieves the information held in the routing table 80 (at 21, 22) togenerate a routing response (at 23) identifying the currently-servingMSC 4. The call is then routed to that MSC 4 (at 24) which, onidentifying that the call is a voice call, instructs the MME 3 tooperate in circuit switched mode (“circuit switched fallback”) (at 25)and connect the call to the base station 2 and ultimately to the userequipment 1 (at 26).

In this prior art system, incoming text messages are handled as shown inFIG. 3. An incoming text message is received by the gateway MSC 6 and arouting request is directed to the destinations user's HSS 5 (at 30),which retrieves the information held in the routing table 80 (at 33, 34)to generate a routing response (at 35) identifying the currently-servingMSC 4. The text message is then routed to that MSC 4 (at 36) which, onidentifying that the call is a text message, instructs the MME 3 tooperate in packet switched mode (at 37) and transmit the text message tothe base station 2 and ultimately to the user equipment 1 (at 38).

A first embodiment will now be described with reference to FIGS. 4, 5,6, 11 and 12. As will be seen by comparison with the previous threefigures, the principal differences in the architecture are the presenceof a second mobile switching center 7, and associated VLR 70, formanaging text messages. In this embodiment the standard MSC 4 is onlyrequired to handle connections which require a circuit switchedconnection, in particular voice messages. In addition the mobilemanagement entity 3 includes an additional service-aware attachmentfunction 39, and the Home Subscriber server 5 includes an additionalservice-aware routing function 59.

In this embodiment, the signaling flow operates as follows, withreference to FIGS. 4, 5 and 6.

FIG. 4 depicts the information flows on attachment of a mobile terminal1 to an eNB 2, and FIG. 11 depicts the operation of the Service Awareattachment function 39 in the MME 3 and the service-aware routingfunction 59 in the HSS 5. In response to the standard attachment request10 sent from the UE 1, by way of the eNB 2 to the mobile managemententity (MME) 3, the Service Aware attachment function 39 in the MMEforwards the IMSI attach request to both the “default” MSC 4 (at 16) andthe SMS MSC 7 (at 42). The second attachment request 46 includes a flagidentifying it as for use with text messaging services.

Each MSC 4, 7 then transmits a respective location update 17, 47 to theHSS 5, the update 47 generated by the SMS MSC 7 again including a “flag”to indicate that this MSC is specific to text services. Theservice-aware routing function in the HSS 5 then updates its internaltable 89 to map the IMSI number to the default MSC 4 and to theSMS-specific MSC server 7.

FIG. 5 depicts the information flows in this embodiment when a request20 for connection of a voice call is received at the gateway MSC 6, andthe left hand side of FIG. 12 depicts the operation of the Service Awarerouting function 59 of this embodiment. The process is similar to thatof the standard procedure depicted in FIG. 2. The Service-aware routingfunction 59 is set to determine whether the incoming routing request ismarked as a text message (at 200) and, recognizing the routing request20 as not relating to a text message, selects the “default” MSC server 4from the routing table 89 (at 21, 22), causing the call connectionprocess 23, 24, 25, 26 to proceed as normal.

FIG. 6 and the right hand side of FIG. 12 depict the operation of thisembodiment when an incoming text message is received at the gateway MSC6. A conventional routing request 30 is directed to the destinationuser's HSS 5. However, unlike the prior art situation depicted in FIG.3, the HSS has a Service-aware routing function 59 which recognizes thetext message 30 as relating to a data service (at 200) and thereforeretrieves the information relating to the SMS-specific server 7 from therouting table 89 (at 63, 64), and generates a routing response 65 to thegateway MSC, identifying the text server 7 instead of the default server4. The text message is then routed to that MSC 7 (at 66) and the MME 3(at 67) to forward the text message to the base station 2 and ultimatelyto the user equipment 1 (at 68). By routing the text message by adedicated (4G) MSC the text message can be delivered without having touse the circuit-switched fallback capability inherent in the operationof the default MSC 4.

A second embodiment will now be described with reference to FIGS. 7, 8,9 and 10, 13 and 14 using an evolved packet core (EPC) architecture. Inthis embodiment the conventional MME 3, MSC 4, and HSS 5 are present,but instead of having the respective service-aware attachment function39 and the service-aware routing function 59 installed, they are nowconfigured to interact through a dedicated server 9 which provides boththe service-aware attachment function and the service-aware routingfunctions (hereinafter referred to as SAARF). It therefore replaces someof the functions of the MME 3 and HSS 5.

FIG. 7 and FIG. 13 depict the attachment process of this secondembodiment when a user terminal 1 first attaches to a base station 2.The process begins with the user equipment 1 sending a standardattachment request 10 to the base station 2, which is forwarded to themobile management entity 3. In this embodiment, the attach request isnot forwarded directly to the Mobile Switching Center 4, but to theService-aware attachment and routing function server 9 (at 72). TheSAARF server 9 queries the HSS 5 (at 72) to identify the MSISDN numberassociated with the IMSI number in the attachment request, and theresponse from the HLR (73) contains the MSISDN number. (Note that inthis embodiment the HSS 5 is only required to maintain this concordance:routing updates are carried out by the SAARF server 9, as will bedescribed later).

The SAARF server 9 transmits a message 75 to an associated database 98to indicate that the UE 1 identified by MSISDN _1 is attached to anevolved packet core (EPC) MME 3 and this information is stored in arouting table 99. If the IMSI attachment request comes from an MME 3which is not EPC-compatible the service-aware attachment and routingfunction 9 does not set the EPC flag in the database 98.

The IMSI attach is then forwarded on to the MSC 4 (at 76) in a similarmanner to the attach procedures 16, 46 described with reference to FIGS.1 and 4, and the HSS 5 is similarly updated (at 77).

In this embodiment, incoming voice calls are handled as depicted in FIG.8 and the left hand side of FIG. 14. The gateway MSC 6 transmits arouting request 20 to the attachment and routing server 9. The server 9identifies the call as a voice call, and which refers the routingrequest to the HLR (at 81) and receives a response indicating theappropriate MSC 4 (at 82), which is communicated to the gateway MSC 6(at 83) which then connects the call as a standard circuit switchedfallback connection (at 24, 25, 26).

Incoming SMS text messages are handled in two different ways, dependingon whether an EPC attachment has been recorded in the database 98. Theseare depicted in FIGS. 9 and 10, and the right hand side of FIG. 14. Asshown in both FIG. 9 and FIG. 10, an SMS routing request 30 is sent fromthe gateway MSC 6 to the SAARF server 9, which searches the record 99 ofthe user terminal 1 in the database 98 (at 91) to identify whether theEPC flag is set, and receives either a negative response (920, FIG. 9)or a positive response 921 (FIG. 10). If the response is negative (FIG.9), the SAARF server continues with delivery of the text messagefollowing the standard procedure depicted in FIG. 3 (at 33-38), theSAARF server itself operating as a standard HSS 5. However, if thereturn 921 indicates that the EPC flag is set (at 921), the SAARF server9 recognizes that the user terminal 1 has been attached using theprocess of FIG. 7 (see 72). It can therefore forward the incoming textmessage directly to the MME 3. It generates a routing response 95 to thegateway MSC 6 requesting the text message itself be routed to the SAARFserver and, on receiving the message 96 it forwards it to the MME 3 (at97) and thus to the user terminal (at 68).

Insofar as embodiments of the disclosure described are implementable, atleast in part, using a software-controlled programmable processingdevice, such as a microprocessor, digital signal processor or otherprocessing device, data processing apparatus or system, it will beappreciated that a computer program for configuring a programmabledevice, apparatus or system to implement the foregoing described methodsis envisaged as an aspect of the present invention. The computer programmay be embodied as source code or undergo compilation for implementationon a processing device, apparatus or system or may be embodied as objectcode, for example.

Suitably, the computer program is stored on a carrier medium in machineor device readable form, for example in solid-state memory, magneticmemory such as disk or tape, optically or magneto-optically readablememory such as compact disk or digital versatile disk etc., and theprocessing device utilizes the program or a part thereof to configure itfor operation. The computer program may be supplied from a remote sourceembodied in a communications medium such as an electronic signal, radiofrequency carrier wave or optical carrier wave. Such carrier media arealso envisaged as aspects of the present disclosure.

It will be understood by those skilled in the art that, although thepresent invention has been described in relation to the above describedexample embodiments, the invention is not limited thereto and that thereare many possible variations and modifications which fall within thescope of the invention.

The scope of the present invention includes any novel features orcombination of features disclosed herein. The applicant hereby givesnotice that new claims may be formulated to such features or combinationof features during prosecution of this application or of any suchfurther applications derived therefrom. In particular, with reference tothe appended claims, features from dependent claims may be combined withthose of the independent claims and features from respective independentclaims may be combined in any appropriate manner and not merely in thespecific combinations enumerated in the claims.

1. A communications routing management entity for a communicationsnetwork arranged to respond to a routing request relating to a useridentity by retrieving a routing instruction from a database of routinginstructions, wherein the communications routing management entity isarranged to distinguish between a first type of requested communicationsconnection and a second type of requested communications connection, toretrieve a first routing instruction associated with the first type ofrequested communications connection and to retrieve a second routinginstruction associated with the second type of requested communicationsconnection.
 2. A communications management entity according to claim 1,wherein the first type of communications connection is carried by acircuit-switching protocol and the second type of communicationsconnection is carried by a packet-switching protocol.
 3. Acommunications management entity according to claim 1, configured todirect voice calls to the first communications connection and to directtext messages to the second communications connection.
 4. A systemcomprising: a communications management entity according to claim 1; andan attachment management entity arranged to process an attachmentrequest received from terminal equipment to cause a location update tobe performed in a service register associated with the terminalequipment, and arranged to perform a service-aware attachment functionto cause the service register to associate the user identity with two ormore alternative routing managers, each appropriate for a respectivetype of incoming communication service types, wherein the communicationsmanagement entity and the attachment management entity are arranged tointercept attachment requests directed from a mobility management entityto a home subscriber server, and to intercept routing requests directedfrom a gateway mobile switching center to a home subscriber server, inorder to perform attachment and routing processes adaptable to differenttypes of requested service.
 5. A communications management entityaccording to claim 1, incorporated in a home subscriber server entityarranged for generation of routing instruction.
 6. A method forprocessing a routing request relating to a user identity, the methodcomprising: by a communications routing management entity:distinguishing between a first type of requested communicationsconnection and a second type of requested communications connection;associating respective first and second routing instructions associatedwith the user identity with the first and second types of requestedcommunications connection; and in response to a routing request inrespect of the user identity for one of the first or second types ofcommunications connections, retrieving the routing instructionassociated with the respective type of requested communicationsconnection from a database of routing instructions.
 7. A methodaccording to claim 6, wherein the user identity is associated with afirst default mobile switching center to which circuit switched trafficis routed and a second mobile switching centre to which packet switchedtraffic is routed.
 8. A method according to claim 6 wherein, in responseto a routing request relating to the user identity, a routinginstruction is retrieved from a database of routing instructions, inwhich a first routing instruction is retrieved in response to a firsttype of requested communications connection and a second routinginstruction is retrieved in response to a second type of requestedcommunications connection.
 9. A method according to claim 6, wherein thefirst type of communications connection is carried by acircuit-switching protocol and the second type of communicationsconnection is carried by a packet-switching protocol.
 10. A methodaccording to claim 9, wherein voice calls are directed to the firstcommunications connection and text messages are directed to the secondcommunications connection.